Reset mechanism for a stack switch which avoids closed circuit condition when a tripping condition prevails



Dec. 12, 1967 E s. ARLIN 3,358,095

"' RESET MECHANISM FOR A STACK SWITCH WHICH AVOIDS CLOSED CIRCUIT CONDITION WHEN A TRIPPING CONDITION PREVAILS Filed April 4, 1966 33 Hill-"HUI i Hm-"NIH I INVENTOR. EDWARD S. ARLI N ummmm 'gaam h United States Patent C) 3,358,095 RESET MECHANISM FOR A STACK SWITCH WHICH AVOIDS CLOSED CIRCUIT CON- DITION WHEN A TRIPPING CONDITION PREVAILS Edward S. Arlin, Norwalk Township, Ohio, assignor t Norwalk Thermostat Company, Norwalk, Ohio, a corporation of Ohio Filed Apr. 4, 1966, Ser. No. 539,795 3 Claims. (Cl. 200-67) ABSTRACT OF THE DISCLOSURE A resettable switch which insures an open circuit be tween its terminals during the reset operation. Four blades are mounted from a common support column to sustain a pair of contacts in a snap-action assembly and a pair of normally closed circuit breaking contacts. In resetting the switch, the reset actuator is arranged to engage, initially only a blade of the circuit breaking contacts to insure that all resetting displacement of the snap-action assembly is preceded by a contact opening displacement of the circuit breaking contacts.

This invention relates to electrical switches and more particularly to switches which have a reset mechanism.

Certain control applications require safety functions wherein the existence of a predetermined condition disables the system as by opening a switch in the electrical circuits associated with its controls. In order to insure safe conditions the tripped switch is arranged to restore the circuit only in response toa resetting operation. It is desirable to avoid restoration of. the circuit both during the resetting function and in the event that the tripping condition prevails. Heretofore, complex interlocks have been employed in an effort to achieve such characteristics. When relatively simple switches have been applied they frequently can be operated falsely whereby under certain conditions a reset can be accomplished by certain reset manipulations to either close the switch contacts before resetting has been completed or close those contacts when the tripping condition persists.

An object of this invention is to simplify and to improve resettable switches. A particular object is to insure against the false closure of a tripped switch under all resetting conditions for that switch.

Another object is to close a resettable switch only at the termination of a resetting opreation and only after the tripped element thereof has been reset and freed of all'constraints which could serve to prevent a normal tripping of the switch.

A feature of this invention enabling achievement of the above objects is a composite switch arrangement wherein the reset actuator opens a switch mechanically independent of the tripped switch and electrically in series therewith at the moment its resetting function is initiated and retains that switch open through the entire reset manipulation.

Another feature of this invention resides in an arrangement of switches which comprise a first switch opened throughout all reset manipulations for a second switch and over a range of displacement of the reset mechanism which encompasses and extends beyond the displacement required to complete the resetting operation of the second switch at both the initiation and termination of said reset. i

A third feature involves the organization of switching elements to include a snap action assembly including a contact in a switch which has a stable reset state and a stable tripped state spaced by a region in which it is unstable and which can be displaced from its tripped state to its reset state by displacement of a resetting blade which carries a first disabling contact in circuit with the switch. A second disabling contact cooperating with the first disabling contact is so oriented with respect thereto that during displacement of the resetting blade the switch being reset by the blade is disabled until the resetting blade is returned to a position free of the reset snap action assembly. It is contemplated that this system is applicable to switches tripped to the closed position from an open condition wherein the disabling contacts are parallel to the tripped switch and maintained closed until reset manipulation of the resetting blade is concluded and are then opened. In the following detailed disclosure, however, the invention is illustrated as applied to a switch tripped from the closed to the open condition and the disabling contacts are in series with the tripped switch and are maintained open until reset manipulation of the resetting blade is concluded and are then closed.

The above and additional objects and features of this invention will be more fully appreciated from the following detailed description when read with reference to the accompanying drawing wherein:

FIG. 1 is a side elevation of a switch embodying the invention and comprising a resettable snap action switch actuated by a thermal time delay, the switch being shown in the tripped condition;

FIG. 2 is a side elevation of the switch of FIG. 1 as it appears during the resetting operation; and

FIG. 3 is a side elevation of the switch in its reset condition.

In the drawing a switch assembly is made up of a stack 11 of elements mounted on a rivet 12 having a shank (not shown) extending through suitable apertures in the elements and swaged over as at 13 to secure the elements. The switch circuit extends from terminal 14 through resilient blade 15 carrying a first disabling contact 16, to a second disabling contact 17 on resetting blade 18. Insulating bushings 19 electrically isolate electrically coupled terminal 14 and blade 15 from the rivet 12 and conductive elements of the stack such as blade 18 by spacing the faces of such elements and fitting internal spacing shanks (not shown) within the apertures of the elements which permit them to be fitted on the rivet to space the edges of those apertures from the rivet shank. The remaining conductive elements of the stack can be isolated electrically by similar bushings. Blade 15 is formed to provide a bias toward blade 18. Blade 18 is offset toward blade 15 to provide clearance for the snap action assembly 21 for purposes to be discussed.

Blade 18 is electrically coupled to snap assembly 21 by abutment in the stack 11 with the several elements of the assembly. A pivoted snap action blade 22 is included in the resettable switch circuit. Contact 23 on blade 22 engages an actuating contact 24 which is screw mounted in a tapped bushing 25 secured to bimetal blade 26. Main terminal 27 abuts blade 26 in the stack 11 to complete the switch circuit. It will thus be seen that the switch is comprised of a snap action switch in series with a switch which is termed a disabling switch.

Actuation of the snap action switch is by a thermal time delay derived from a heater 28 mounted in bimetal blade 26 and supplied through leads 29 and 31 with current characteristic of the conditoin to which the switch is responsive. Heater current is coupled to the leads 29 and 31 through terminals 32 and 33 in the stack 11. The switch is intended to sense and respond to low power levels such as 0.4 watt sustained for a given interval. This power dissipated in heater 28 raises the temperature of bimetal blade 26 causing it to flex upward at its outer end as viewed in the drawings. Such flexure trips the blade 22 to cause it to travel from the position of FIG. 3 to the position shown in FIG. 1 thereby opening the circuit.

Snap action assembly 21 is of the over center type. Blade 22 is bifurcated so that two legs 34 straddle a tension spring 35 coupled at 36 to the outer end of blade 22 and at 37 to a blade 38 in stack 11. Ears 39'extend outwardly from legs 34 to engage their edges most proximate the stack 11 in sockets 41 to form fulcrurns upon which the blade 22 pivots. The snap action relies upon the relationship of the line of tension along the axis of spring 35 between its couplings 36 and 37, and the lines of compression between those couplings and the pivots at 41. When the pivots 41 are above the tension axis of spring 35, the outer end of blade 22 and contact 23 are biased upward to the position shown in FIG. 1. When the pivots 41 are below the tension axis of spring 35 the contact 23 is biased against contact 24 to close the switch.

Since only a slight relative displacement of actuator 24 relative to pivot point 41 should be utilized to trip blade 22 where the switch is to respond to low levels of power, the relative positions of the pivot point and actuator should be established precisely and should be retained over the range of ambient conditions to which the switch assembly is subjected. Actuator 24 is adjustable relative to bimetal blade 26 through its threaded mounting. Ambient temperature compensation for pivots 41 is provided "by forming them from the tabs 42 at the bifurcated end of bimetal blade 43 and bent generally at a right angle to that blade. Blade 43 shifts in response to ambient temperature in the manner of blade 26 so that ambient temperature increases cause both blades to displace their outer ends upward a corresponding amount.

In resetting the snap action switch blade the disabling contacts 16 and 17 are opened before the snap action reset is initiated. The illustrative embodiment shows blade 22 stopped against blade 18. The switch is equally satisfactory it blade 22 is stabilized in its tripped position by other means such as a stop limiting travel of the legs 34 or the binding of the upper side of spring 35 against the face of bimetal blade 43 between ears 42. When the latter form of limit is elfective to space blade 22 from blade 18 while it is at its stable tripped position, contacts 16 and 17 are opened by downward displacement of resetting blade 18 even before the resetting blade engages the end of blade 22 and initiates movement of the pivoted blade 22 toward its reset position.

With disabling contacts 16 and 17 open, the further advance of resetting blade 18 toward actuator 24 causes the outer end of blade 22 to move toward actuator 24 and carry the tension axis of spring 35 into coincidence with and then below the pivot axis 41. Spring 35 then biases blade 22 downward and contact 23 in abutment with contact 24. In this stable reset state of blade 22 as shown in FIG. 2, the circuit between terminals 14 and 27 remains opened since disabling contacts 16 and 17 are open. Thus no false operation of the switch can occur during reset as by only partially releasing the reset actuator to hold blade 22 from its stable tripped position and in contact with actuator contact 24 since the disabling contacts cannot be closed until resetting blade is in its fully retreated position. This full reset condition is shown in FIG. 3.

It will be noted that the actuator for restting blade 18 does not form a part of the switch assembly. Rather it is illustrated only in FIG. 1 as a plunger 45 extending through a bushing 46 in the wall of housing 47 (shown only fragmentarily). Plunger 45 can be biased to its illustrated position by the resilience of blade 18 bearing against its actuating end 48. Its stroke can be restricted in length by the length of the exposed shank protruding from bushing 46 and can be limited to reciprocation generally normal to the blade 18 in its most relaxed position and in the plane of travel of the blade 18 and that of blade 22.

Alternative forms of compound switches. wherein disabling contacts are actuated throughout all resetting operations are contemplated. In these forms of switches different techniques can be employed to cause the tripping of the resettable blade from a stable reset position to a stable tripped position spaced therefrom over a region of blade instability. Thus different snap action assemblies from assembly 21 can be employed. Further different mechanisms for resetting might be utilized in a compound switch structure as where the blade to be reset is drawn to its reset condition magnetically by a magnet carried on a blade corresponding to blade 18 and carrying a disabling contact corresponding to contact 17.

In view of the variants available on the switch structure set forth, it is to be understood that the preceding detailed description and the drawing are to be read only as illustrative of the invention and not in a limiting sense.

Having described the invention, I claim:

1. A resettable electric switch comprising a support column; a first contact blade insulatingly mounted on said column to extend radially therefrom; a first contact on said blade and spaced from said column; a first terminal engaging said first blade; a second resilient contact blade insulatingly mounted on said column radially aligned with said first blade relative to said column, adjacent said first blade, and mechanically biased toward said first blade; a second contact on said second blade oriented to abut said first contact; an extension on said second blade extending from said column beyond said second contact; a third blade insulatingly mounted on said column to extend radially therefrom; an electrical connecting means between said second and third blades in the vicinity of said column; a fourth blade insulatingly mounted on said column to extend radially therefrom and radially aligned with said third blade relative to said column; a fourth contact mounted on said fourth blade and spaced from said column; a snap-action assembly mounted on said third blade in electrical communication therewith said snap-action assembly having an actuated portion remote from the point at which it is mounted on said third blade; a third contact mounted on said actuated portion of said snap-action assembly to engage said fourth contact while in a first stabile position of said snap-action assembly; said snap-action assembly having a second stabile position with said actuated portion abutting said extension on said second blade; a second terminal engaging said fourth blade; means for displacing the portion of said fourth blade mounting said fourth contact whereby said snap-action assembly is transferred from said first to said second stabile position; and shiftable means having a terminal portion abutting said extension'on said second blade for displacing said second blade from said first blade and toward said third blade and transferring said snap-action assembly from said second stabile position to said first stabile position, whereby operation of said shifting means opens the circuit between said first and second terminals at said first and second contacts for all positions of said shifting means which are effective for shifting said snap-action assembly.

2. A combination according to claim 1 wherein said means for displacing said fourth blade is responsive to heat applied to said fourth blade to shift the position of said fourth blade toward said third blade for'chan-ges in temperature of a first sign and away from said first blade for changes in temperature of a second sign; said combination including means to displace said third blade References Cited toward said fourth blade for changes in temperature of UNITED STATES PATENTS said second sign and away from said first blade for changes in temperature of said first sign, whereby said 2191588 2/1940 Satfler 200116 snap-action assembly is shifted in position for ambient 5 2804524 8/1957 Dahien 2O0' 138 temperaturecompensation 2,854,548 9/1958 Cass1dy 200-422 3. A combination in accordance with claim 1 wherein 3,215,802 11/1965 Newman 2OO 114 3,236,971 2/1966 Cotsworth 200114 said third blade is a bimetallic blade which deflects with temperature changes and said means for displacing said I fourth blade is a bimetallic blade which is shifted in posi- BERNARD GILHEANY "nary Exam" tion With temperature changes. H. A. LEWITTER, Assistant Examiner. 

1. A RESETTABLE ELECTRIC SWITCH COMPRISING A SUPPORT COLUMN; A FIRST CONTACT BLADE INSULSTINGLY MOUNTED ON SAID COLUMN TO EXTEND RADIALLY THEREFROM; A FIRST CONTACT ON SAID BLADE AND SPACED FROM SAID COLUMN; A FIRST TERMINAL ENGAGING SAID FIRST BLADE; A SECOND RESILIENT CONTACT BLADE INSULATINGLY MOUNTED ON SAID COLUMN RADIALLY ALIGNED WITH SAID FIRST BLADE RELATIVE TO SAID COLUMN, ADJACENT SAID FIRST BLADE, AND MECHANICALLY BIASED TOWARD SAID FIRST BLADE; A SECOND CONTACT ON SAID SECOND BLADE ORIENTED TO ABUT SAID FIRST CONTACT; AN EXTENSION ON SAID SECOND BLADE EXTENDING FROM SAID COLUMN BEYOND SAID SECOND CONTACT; A THIRD BLADE INSULATINGLY MOUNTED ON SAID COLUMN TO EXTEND RADIALLY THEREFROM; AN ELECTRICAL CONNECTING MEANS BETWEEN SAID SECOND AND THIRD BLADES IN THE VICINITY OF SAID COLUMN; A FOURTH BLADE INSULATINGLY MOUNTED ON SAID COLUMN TO EXTEND RADIALLY THEREFROM AND RADIALLY ALIGNED WITH SAID THIRD BLADE RELATIVE TO SAID COLUMN; A FOURTH CONTACT MOUNTED ON SAID FOURTH BLADE AND SPACED FRO, SAID COLUMN; A SNAP-ACTION ASSEMBLY MOUNTED ON SAID THIRD BLADE IN ELECTRICAL COMMUNICATION THEREWITH SAID SNAP-ACTION ASSEMBLY HAVING AN ACTUATED PORTION REMOTE FROM THE POINT AT WHICH IT IS MOUNTED ON SAID THIRD BLADE; A THIRD CONTACT MOUNTED ON SAID ACTUATED PORTION OF SAID SNAP-ACTION ASSEMBLY TO ENGAGE SAID FOURTH CONTACT WHILE IN A FIRST STABILE POSITION OF SAID SNAP-ACTION ASSEMBLY; SAID SNAP-ACTION ASSEMBLY HAVING A SECOND STABILE POSITION WITH SAID ACTUATED PORTION ABUTTING SAID EXTENSION ON SAID SECOND BLADE; A SECOND TERMINAL ENGAGING SAID FOURTH BLADE; MEANS FOR DISPLACING THE PORTION OF SAID FOURTH BLADE MOUNTING SAID FOURTH CONTACT WHEREBY SAID SNAP-ACTION ASSEMBLY IS TRANSFERRED FROM SAID FIRST TO SAID SECOND STABILE POSITION; AND SHIFTABLE MEANS HAVING A TERMINAL PORTION ABUTTUNG SAID EXTENSION ON SAID SECOND BLADE FOR DISPLACING SAID SECOND BLADE FROM SAID FIRST BLADE AND TOWARD SAID THIRD BLADE AND TRANSFERRING SAID SNAP-ACTION ASSEMBLY FROM SAID SECOND STABILE POSITION TO SAID FIRST STABILE POSITION, WHEREBY OPERATION OF SAID SHIFTING MEANS OPENS THE CIRCUIT BETWEEN SAID FIRST AND SECOND TERMINALS AT SAID FIRST AND SECOND CONTACTS FOR ALL POSITIONS OF SAID SHIFTING MEANS WHICH ARE EFFECTIVE FOR SHIFTING SAID SNAP-ACTION ASSEMBLY. 